Breathing is an innate motor behavior commencing at birth and continuing until the cessation of life. The concerted actions of sensory and motor systems that monitor and adjust the magnitude of ventilation on a breath to breath basis ensure that breathing is commensurate with the oxygen supply and carbon dioxide (CO2) washout. However, the mechanisms involved in coordinating the activity of respiratory rhythm generating neurons with the metabolic demands of the body are not fully understood. Hence the aim of this investigation is to characterize the involvement of inspiratory rhythm-generating neurons in neurochemical control of breathing, specifically inspiratory pacemaker neurons that may be mediating ventilatory responses to CO2/H+ stimulation. The study will focus on rhythmogenic neurons within the pre Botzinger complex as a candidate cell population for CO2/H+ central chemosensory integration. We will specifically describe how respiratory cells respond to pH perturbations occurring in the intra- or extracellular compartments and identify possible membrane mechanisms that contribute to intrinsic chemosensitivity. We will execute electrophysiological and neuroanatomical experiments using in vitro preparations obtained for neonatal rodents. Techniques will include extracellular nerve and single-cell recordings and whole cell perforated patch-clamp. In addition, we will use immunofluorescence, Western blotting, cell culture and in situ hybridization methodologies to define expression of CO2/H+/pH-sensitive substrates within inspiratory rhythm generating neurons. Data obtained from this investigation will provide answers to the fundamental questions related to chemosensory regulation with respect to the contributions of respiratory rhythm generating cells and how dysfunction of this critical population may lead to pathological conditions. These results will have further impact on the understanding of mechanisms occurring in centrally mediated cardiorespiratory dysfunctions such as sudden infant death syndrome (SIDS) and other apneic breathing disorders.